Telephone system



Jan. 19, 1932. T. G. RICE TELEPHONE SYSTEM 2 Sheets-Sheet 1 Filed April14, 1930 1m Thomas %4 7//% E'EUIHEHDE 17- Jan. 19, 1932. T. G. RICE1,842,119

TELEPHONE SYSTEM Filed April 14, 1950 2 Sheets-Sheet 2 Tamil-'-ThumasEenr' ERiuE Patented Jan. 19, 1932 UNITED STATES PATENT orrrcsTHOMAS GEORGE RICE, OF LIVERPOOL, ENGLAND, ASSIGNOR T ASSOCIATED TELE-PHONE & TELEGRAPH COMPANY, OF CHICAGO, ILLINOIS, A CORPORATION OF DELA-WARE TELEPHONE SYSTEM Application filed April 14, 1930, Serial No.443,980, and in Great Britain May 29, 1929.

The present invention relates to telephone systems employing automaticswitches and is more particularly concerned with increasing the speed ofoperation of switches which hunt in two stages.

This is effected according to one feature of the invention by arrangingthat the switches are adapted to hunt in two stages a for the absence ofthe same source of potential.

According to a further feature of the invention the speed of operationis increased by dispensing with the usual magnet interrupter relay andby employing a self-interrupting magnet circuit in conjunction with whatare referred to as double dog springs which operate on each step of theswitch.

According to another feature of'the invention in order to secure a quickchangeover from the primary movement of the switch to the secondarymovement and in order to terminate accurately the secondary movement ofthe switch use is made of a high 25. voltage surge from a highlyinductive windlhe invention will be better understood from the followingdescription of one method of carrying it into efiect, reference beinghad to the attached'drawings, of which Fig.

1 shows a finder switch embodying the new circuit features while Fig. 2shows a finder allotter circuit. It will be understood, however, thatthis is given by way of example only and that various modificationscould be made in the circuit details by those skilled in the art withoutdeparting from the spirit of the invention.

When the calling subscriber removes his receiver to initiate a call linerelay A is energized over a. circuit traceable from earth at armature 10of relay B, calling loop, armature 11, upper winding of relay A tobattery. Relay A thereupon operates and assuming calling subscriber tobe located on the fifth level of the finder switch, the operation ofarmature 12 disconnects the normal earth from the fifth contact of thevertical bank VB in order to mark the level in which the contacts of thecalling line are located.

It will be understood, however, that the dotted conductor shown betweenthe vertical bank VB and the armature 12 represents a series of chaincontacts similar to those associated with armature 12, each set of whichwill be controlled by the line relay of a different sub-station, locatedon the same level.

Due to the operation of armature l3, earth is disconnected from theprivate bank contact of the calling line, in order to provide a stopcircuit to the automatic rotation of the switch.

Returning now to the operation of armature 12, a circuit may be tracedfrom earth, armature 12, resting contact of armature 14,. conductor 15,winding of the start relay S, Fig. 2, to battery, thereby causing therelay to operate and at its armature 16 earth is extended over thefollowing circuit; winding of the switching relay H1 of the first finderallotter F A1, armature 17 interrupter springs 18, winding of thedriving magnet DMl to battery, and in parallel thereto via the windingof the other switching relay H2 of the second finder allotter FA2,armature 19, interrupter springs 20, winding of driving magnet DM2 tobattery.

Consequently, both relays commence to operate over the circuitsdescribed. Belay H1, however, is arranged to be slightly faster tooperate than relay H2 so that upon the operation of this relay theenergizing path to relay H2 will then be opened at armature 19.

At armature 21 a locking circuit is provided to relay H1 independentlyof interrupter springs 18, while at armature 22 the following circuit iscompleted: earth, armature 22, wiper 23 and associated bank contacts ofthe finder allotter FAl, conductor 24, winding of relay G of the finderto battery. Relay G thereupon operates over the circuit traced and firstmakes its light armature 25, thereby completing a circuit from earth atthe resting contacts of the off-normal springs N, armature 25, windingof relay C to battery, this same earth connection is also extended viaarmature 26 and its resting con- 7 tact to the right-hand terminal ofrelay D. When relay G operates fully, earth at arma ture 27 will beconnected to the left hand terminal of relay D so that this relay is nowshort-circuited.

Considering now the operation of relay C over the circuit previouslytraced, it will be seen that the following vertical impulsing circuitwill now become operative; earth at armature 28 of relay C, arn'iature29, armature 30, interrupter springs 31, winding of the vertical magnetV to battery. Accordingly, the vertical magnet V energizes and causesthe shaft and wipers to be raised from the normal position in the wellrecognized manner, and as a result the springs DD which are actuated bythe outward thrust of the so-called double dog, make contact before thevertical interrupter springs 31 break contact. It should be mentioned atthis point that the double dog is moved outwards from the switch shaftwhilst each step is being made and thereby opens the double dog springswhich re-close when the double dog falls into engagement with the nexttooth on the shaft when the step has been completed.

The energizing circuit of the vertical magnet V is thereby held closedafter the interrupter springs 31 have broken, by way of the restingcontact of armature 32, operated springs DD, resting contact of armature33 to the initial energizing circuit. Consequently, when the verticalmagnet V has completed its full stroke, the so-called double dog willthen drop into engagement with the first tooth of the vertical hub onthe switch shaft, thereby allowing the springs DD to open and effect acomplete opening of the vertical magnet circuit. Upon the completerestoration of the vertical magnet interrupter springs 31, a similarsequence of operations will ensue in order to raise the shaft and wipersa still further step.

It must be mentioned that during the first vertical step, that thevertical selecting wiper 3a is arranged to engage with first bankcontact before the off-normal springs are operated, and since thiscontact is normally earthed the short circuiting path to the right-handside of the winding of relay D will be maintained by way of the releasemagnet springs 58, armature 35 and its resting contact and armature 26and its resting contact. Similarly, also relay C will be maintainedoperated over a branch of this circuit. Consequently, since the verticalselecting wiper 34: is arranged to bridge adjacent contacts during itsmovement, the foregoing circuit conditions will then prevail until suchtime as wiper 34 positions itself upon the unearthed fifth bank contact.In this position the short-circuiting path to the right-hand terminal ofrelay D is opened, and as a result the consequent high voltage surgefrom the inductive winding of relay C is then applied via the followingcircuit: battery, winding of relay C, armature 2'6 and its restingcontact, winding of relay D working contact of armature 27 and saidarmature to earth. Relay D is theref re operated very quickly, in orderto open the vertical stepping circuit at armature 30 before the verticalmagnet can again energize; and thereafter locks up from battery viaresistance 36 and armature 37. The operation of relay D also causesearth at armature 38 to be connected by way of the resting contacts ofthe rotary off-normal springs RON, to the right-hand terminal of relayF; and earth at armature 39 to complete a circuit to relay E. Upon theoperation of relay E, earth at armature l0 is connected to the left-handterminal of relay F, while at armature 42 the fol lowing impulsingcircuit is completed to the rotary magnet R, earth at armature 28 ofrelay C, armature 29, armature 42, interrupter springs l3, winding ofrotary magnet R to battery. Hence the wipers of the finder switch willnow be automatically rotated over the bank contacts of the selectedlevel, and here a ain due to the operation of armatures 32 and 33 ofrelay E the springs DD are again bridged across the interrupter contactsin order to ensure that the magnet shall be completely operated.

It must also be mentioned that the rotary testing wiper 44 is arrangedto engage with the first bank contact before the rotary oil'- normalsprings RON open, so that in case the first bank contact should benormally earthed, the short-circuiting path will be maintained to theright-hand terminal of relay F from test wiper 44 by way of the restingcontact of armature 35, and the working contact of armature 26, whilesimilarly, relay C is again maintained via a branch circuit.

Hence the wipers of the switch will be auto matically rotated due to theself-interrupting circuit of the rotary magnet and as the testing wiper4a is also of the bridging type the foregoing circuit conditions willprevail until the wiper 44- positions itself on the desired bank contactwhich is unearthed. In this position, the short-circuiting path to relayF will now be opened and a result relay C will thereupon dischargeitself over the following circuit; battery, winding of relay C, armature26 and its working contact, winding of relay F, armature 40 to earth.Relay F is therefore operated very quickly in a similar manner to relayD, in order to open the rotary impulsing circuit at armature 29 beforethe rotary magnet is able to energize again; and thereafter locks up inseries with relay C via armature 4-0. The operation of relay F causesthe calling loop to be extended via wipers 46 and i7, armatures 48 and49 to the line relay A1 of the first selector, shown schematically atthe righthand side of Fig. 1, and at armature 35 completes the followingcircuit: earth, armature all, working contact of armature 35 and saidarmature, release magnet springs wiper 4A- and bank contact, armature 13and its working contact, lower winding of line relay A in series withcut-off relay B to battery. Relay A therefore remains operated over itslower winding, while the operation of relay B removes the normal batteryand earth connections from the calling loop at armatures 11 and 12 andat armature 14 recompletes the chain marking circuit. At armature 50 ofrelay F, earth is extended over conductor 51 by way of bank contact andwiper 52 of the finder allotter FAl, armature 53 and its workingcontact, armature 17, armature 54, armature 21, winding of the drivingmagnet DMl to battery, with a parallel path from armature 17 andinterrupter springs 18 to the winding of the driving magnet DMl tobattery. Accordingly the magnet energizes and prepares to advance thewipers of the switch F111 onto the next set of bank contacts. Upon theoperation of the cut-off relay B, the holding circuit to the start relayS was opened at armature 14 and as a result the relay releases andcauses earth to be removed from the circuit to relays H1 and H2.

Belay H1 thereupon restores to normal and in turn opens the energizingcircuit to the driving magnet DM1 at armatures 21 and 53 so that thedriving magnet DMl deenergizes and the wipers of the switch will therebybe advanced onto the next set of bank contacts in the well recognizedmanner, in order to prepare the next idle find-er circuit in readinessfor the initiation of the next call. Due to the disconnection of earthfrom conductor 24 by the movement of wiper 23, the circuit of relay G isopened whereupon this relay releases and is followed by the release ofrelays D and E in succession.

Returning now to the operation of relay F, it will be remembered that aloop circuit was extended to the line relay A1 of the first selector,thereby causing the said relay to be operated; relay A1 in turncompletes the usual local circuit to the release relay B1.

Upon the operation of the release relay B1, earth at armature 55 isconnected by way of the release trunk conductor to the left-handterminal of relay F, and since relays G, D and E have released due tothe stepping of the earthed wiper 23 as previously mentioned, relays Fand C will then be maintained energized in series throughout theremainder of the call. in the following circuit: battery, winding ofrelay C, armature 45, winding of relay F, armature 55 to earth. Relays Aand B are maintained energized in series over the following circuit:battery, winding of relay B, lower winding of relay A, front contact ofarmature 13 and said armature, wiper 44, release magnet springs 58,armature 35 and it front contact, armature 55 and its front contact toearth. The dialled digits are then received from the calling subscriberover the loop circuit to the line relay A1, and in response thereto thewipers of the switch are raised to the desired level.

Upon the release of the connection when both subscribers replace theirreceivers on the switch hooks, earth will be removed off the releasetrunk conductor by the last switch in the train, and in consequencethereof the series holding circuit to relays F and O is opened. Upon therelease of relay C the following circuit is completed to the releasemagnet Z; earth, armature 27 of relay G and its resting contact,armature 56 and its resting contact, operated contacts of oil-normalsprings N, winding of release magnet Z, conduetor 57, winding of lowresistance total calls relay TO to battery. The release of the switchnow takes place in the well recognized manner, while the operation ofthe release magnet springs 58 serves to disconnect the vertical androtary testing wipers during their reurn motion over the banks. Relay TCis also operated over the circuit traced, and at its armature 59 extendsearth over conductor 60 in order to eifect the registration of the callon the total calls meter. In case the condition should arise where allthe finders are engaged at a given instant, common conductor 61 willthen be found to be free of earth due to the operation of all thevarious sets of off-normal springs similar to N in Fig. 1, and as aresult a convenient stop circuit is thus provided at the twenty fifthand first bank contacts respectively of the finder allotter FAl and FA2,thereby preventing the continuous rotation of these switches during thebusy condition. Consequently, should a still further call be receivedduring the all finders busy condition; upon the operation of relay H1earth will then be connected at armature 22, by way of wiper 23 and 25thbank contact over conductor 62 to an overflow meter, thereby registeringthe call as lost because all the finders of the group were busy at thetime it was made.

v 1. For use in telephone or like systems an automatic hunting switchthe continuance of the hunting operation of which is dependent upon theconnection of a particular potential to the contacts engaged by the testwiper in which the absence of said potential causes a source of highvoltage to be connected up independently of said wiper to terminate thehunting operation- 2. An automatic hunting switch for use in telephoneor like systems in which a highly inductive winding is adapted to beconnected in series with the relay which operates when a connection isextended to a wanted line to increase the speed of operation of saidrelay, this relay being shunted by potential picked up over the testWiper as long as unwanted lines are encountered.

3. An automatic hunting switch for use in telephone or like systemsarranged to hunt in two directions for the absence of predeterminedpotential in which a highly inductive winding is adapted to be connectedin series with the relay which operates at the end of the primaryhunting movement and subsequently to be connected in series with therelay which operates at the end of the secondary hunting movement inorder to increase the speed of operation of the relays.

4. A finder switch for use in telephone or like systems adapted to huntover a plurality of contacts each corresponding to a group of lines inwhich a series circuit for each of said groups normally connects asource of potential to each of said contacts, and means for opening saidcircuit when a line in the corresponding group of lines is calling.

5. A step-by-step hunting switch for use in telephone or like systems astepping magnet of the switch having contacts for interrupting its owncircuit in which springs operated by each step of the switch maintainthe circuit of said magnet closed until the switch has stepped.

6. A hunting switch as claimed in claim 5 in which said springs arecarried by the retaining pawl which is intermittently moved during thesetting motion by sliding over the teeth on the switch shaft.

7. In a telephone system, an automatic switch having a test wiper, testcontacts accessible to said wiper and having a particular potentialnormally connected thereto, means for initiating the hunting operationof said switch, means for continuing the said hunting operationdependent upon said wiper engaging said contacts having said potentialconnected thereto, and means in said switch responsive to said wiperengaging one of said contacts characterized by an absence of saidpotential for connecting up a source of high voltage independently ofsaid wiper to terminate the hunting operation.

8. In a telephone system, an automatic switch having a test wiper, testcontacts accessible to said wiper and having a particular potentialnormally connected thereto, means for initiating the hunting operationof said switch, means for continuing the said hunting operationdependent upon said wiper engaging said contacts having said potentialconnected thereto, a switching relay in said switch for terminating thehunting operation, acircuit for energizing said relay including aninductive winding connected in series with said relay for increasing thespeed of operation of said relay, and a circuit for shunting said relayduring the hunting operation only as long as said wiper engages contactshaving said particular potential connected thereto.

9. In a telephone system, an automatic switch having means for huntingin two directions for the absence of a predetermined potential, achangeover relay for terminating the primary hunting operation, aswitching relay for terminating the secondary hunting operation, and aninductive winding connected in series with the changeover relay forincreasing the speed of operation of said relay at the end of theprimary hunting movement and subsequently connected in series with theswitching relay for increasing the speed of operation of said relay atthe end of the secondary hunting movement.

10. In a telephone system, an automatic switch having means for huntingin two directions for the absence of a predetermined potential, achangeover relay for terminating the primary hunting operation, aswitching relay for terminating the secondary hunting operation, aprimary test wiper in said switch for preventing the operation of saidchangeover relay by shunting said relay as long as said wiper encounterssaid predetermined potential, a second test wiper in said switch forpreventing the operation of said switching relay by shunting said relayas long as said wiper encounters said predetermined potential, and aninductive winding connected in series with the changeover relay forincreasing the speed of operation of said relay at the end of theprimary hunting movement and subsequently connected in series with theswitching relay for increasing the speed of operation of said relay atthe end of the secondary hunting movement.

11. In a telephone system, an automatic switch, primary and secondarytest contacts in said switch having the same particular potentialnormally connected thereto, means for removing said potential from aparticular primary and a particular secondary test contact, and meansfor operating said switch in two hunting movements in search of theprimary test contact and the secondary test contact characterized by theabsence of said potential.

12. In a telephone system, a group of lines divided into subgroups, atest contact for each subgroup, a series circuit in each subgroupnormally connecting a source of potential to their respective contacts,means for opening the series circuit of a subgroup when a line thereinis calling, a finder switch, and means for operating said finder switchin search of the contact having said potential removed therefrom by theopening of said series circuit.

13. In a step-by-step hunting switch, a stepping magnet for operatingsaid switch step-by-step, a circuit for operating said magnet, contactson said magnet for interrupting said circuit, another circuit "for saidmagnet, and springs operated upon each step of said switch for closingand maintaining said other circuit independent of said first circuituntil said switch has stepped.

14. In a step-by-step hunting switch having a switch shaft and aretaining pawl therefor, a stepping magnet for operating said switchshaft step-hy-step, a circuit for operating said magnet, contacts onsaid magnet for interrupting said circuit, another circuit for saidmagnet, means on said switch shaft for operating said pawl on each stepof the shaft, and springs operated by said pawl upon each step of saidshaft for closing and maintaining said other circuit until said shafthas completed its step.

15. In a telephone system, an automatic hunting switch having a testwiper, means for initiating the hunting operation of said switch, meansfor continuing the hunting operation dependent upon said wiperencountering a predetermined potential, a relay in said switch forterminating said hunting operation, a second relay in said switch havinga high inductive winding connected in series with said first relay forincreasing the speed of operation of said first relay, means forcontinuously holding said second relay energized over said winding andfor preventing the operation of said first relay by shunting said firstrelay during the hunting 5 operation only as long as said wiperencounters said potential.

In testimony whereof I aifix my signature.

THOMAS GEORGE RICE.

